The weights used by bodybuilders and weight lifters typically include a bar or shaft of several feet in length with a rotatable, knurled sleeve slipped over the central portion of the bar and with fixed stops at the opposite ends of the sleeve. Disc-like weight plates with central openings are loaded onto opposite ends of the bar and are secured in position against the stops by a pair of collars. Various sizes and numbers of weight plates are used to obtain a desired total weight. The plates are changed frequently because different weights are required during a succession of lifts or for different exercises or for different individuals.
Because the weight plates are changed frequently during use, the collars which hold them in position on the bar must be easily put on and taken off, preferably without the use of any tools. On the other hand, the collars must hold the weight plates securely in position because accidental slipping or dropping of the weight plates can result in personal injury and property damage.
The most commonly used collar for weight lifting includes a bushing with a bolt or screw which passes through a threaded hole and frictionally bears against the bar. The collar is secured in place by tightening the bolt against the bar. The bolt can be tightened with a tool or may have an L-shaped extension for manual tightening. Collars of this type have a number of disadvantages. The bolts frequently loosen, allowing the weight plates to slip on the bar or to fall off the bar. The bolts are difficult and inconvenient to tighten in a secure manner. In addition, when the bolts are fully tightened, they often dig into and damage the bar. Other prior art collars include a two-piece bushing with bolts on opposite sides of the bar, similar to a pipe clamp. These collars don't damage the bar. However, the inconvenience of tightening bolts remains. With collars using the friction of a manually-tightened bolt, the clamping force depends on the extent to which the bolt is tightened and may be insufficient.
British patent application Ser. No. 2,151,493A by Marcy Gymnasium Equipment Co., published July 24, 1985, discloses a weight clamping arrangement for a barbell wherein locking ball members are engaged in grooves in the bar. Quick release mechanisms are also disclosed in U.S. Pat. Nos. 4,395,051 to Tanamura and 4,453,449 to Holman.
Quick release collars have been described above in connection with weight lifting barbells. However, quick release collars have a wide variety of applications where quick release and secure holding with a moderate amount of force are required. Examples of such applications are in tire changers used in service stations, spare tire retention devices for automobiles, retention of wheels on toys, wagons and the like, and for adjustable telescoping devices such as projection screens, drafting tables and beach umbrellas.
It is a general object of the present invention to provide a novel quick release collar for use on a bar or shaft.
It is a further object of the present invention to provide a quick release collar which is easily and manually removable without tools and without turning the collar on the bar.
It is a further object of the present invention to provide a quick release collar which stays securely in position on a bar without damaging the bar.